Unless you run your own BlackBerry Enterprise Service in-house there is no guarantee of secure communications between your smartphone and the server. The latest generation of forensic software can decrypt the contents of a BlackBerry 10 smartphone and even brute force a device password in minimal time. Assume the government is monitoring all traffic.

What this means that as a stand alone device without any encryption it can be accessed for its data.

If you have a BES account and the admin allows access it can be accessed for its data.

If you have an "In House" service where you do not have to give the keys then you may be safe on the Enterprise side of the device.